Yes, I agree with that. Same time it's applicable to any BJT, Darlingtons just have saturation little bit higher than others. So the trade is TIP120 + heatsink or MOSFET + TC426.

No, the trade for medium current (a small number of amps) is TIP120 + heatsink or logic level mosfet + series resistor. You only need a mosfet driver if you are switching much larger currents than the TIP120 can handle, or are using fast PWM (which the TIP120 wouldn't handle well anyway).

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You only need a mosfet driver if you are switching much larger currents than the TIP120 can handle, or are using fast PWM

Not quite. Logic level P-channel MOSFET has high Gate Threshold Voltage (example, SFE FQP27P06) and again you need a driver IC (charge pump voltage multiplier) for 3.3V uCPU. Darlington TIP127 has no trouble with voltage as low, as 2V at the base.

I wish I had equipment to solder SMD components, microscope, re-flow oven etc. Or I had a job with all this stuff at my convenience. But than again, 'd I have time to play with arduino and visit this forum?

Yes, it's a shame that a lot of the best components are only available in SMD packages. I bought a batch of SMD-to-DIP adapters (readily available from Sparkfun, Futurelec, eBay etc.) a while ago so that I can use them with breadboards and stripboard for prototyping. I don't use a reflow oven to solder them, just a hotplate. The larger SMD devices can be soldered using a fine-tipped soldering iron.

Formal verification of safety-critical software, software development, and electronic design and prototyping. See http://www.eschertech.com. Please do not ask for unpaid help via PM, use the forum.